Recently small portable devices such as a mobile phone, note-type personal computer and personal digital assistant (PDA) are frequently utilized. Applications of these devices are spreading and conveniences of users' are increasing with a development of network systems and software. Then requirements are increasing for high-performance devices to communicate information precisely using vibration or sonic wave, and quality improvements are expected for vibration components such as a oscillator, vibration sensor or touch sensor and audio equipments such as a speaker, microphone or receiver. As for vibrators, characteristics such as a small size, light weight and low power consumption are being developed and a range of its use is increasing.
To downsize and save power consumption of the vibrators, driving sources to replace conventional electromagnetic actuators are now being developed. An electromagnetic actuator consisting of a permanent magnet and a voice coil is not suitable to mount on a mobile electronic device such as a mobile phone because it does not save electric power since the voice coil needs much current when actuating and it is difficult to downsize the actuator due to structural problems. Thus efforts are made for development of a vibrator using a piezoelectric actuator as a driving source having a feature of a small size, light weight and low power consumption.
On the other hand, a vibrator is expected to stimulate ones skin or hand palm by a mechanical vibration and use for a communication tool of information with a stereoscopic effect and affinity by contact feeling of the vibration produced simultaneously with a telephone call as well as for a notice of the call.
In a mobile electronic device (designated as “mobile device” hereinafter) such as a conventional mobile phone, personal digital assistant or game equipment, a means of information transmission to a user is utilized such as a visual method by a display, auditory method by a speaker, etc, or contact feeling method by a vibrator (actuator). Particularly, an information transmission method is developed which utilize the contact feeling with interaction of visual sense or auditory sense. For example, a method to produce a vibration by an actuator in connection with a display is known for its effect of enhancing affinity and stereoscopic effect by a combination of the contact feeling and visual sense. On the other hand, a game machine is put to practical use that provides high ambience by producing vibration together with movements of subjects such as persons, animals or vehicles on a display.
Patent Document 1 discloses a contact feeling generator to convey the contact feeling to a player in connection with movements on a display of a video game, etc. Patent Document 2 discloses an example of an electronic device using a piezoelectric actuator as a vibration component, in which a plurality of piezoelectric actuators are provided on the case of the electronic device and information is transmitted to a user by the vibration of a case produced by the actuator. Patent Document 3 discloses a vibration-type information device to notify a call to a user by auditory sense and contact feeling produced by a piezoelectric ceramic oscillator provided in a pager, etc.
Patent Document 1:
JP Patent Kohyo Publication No. JP-H10-506033A
Patent Document 2:
JP Registered Utility Model No. 3085481
Patent Document 3:
JP Patent Kokai Publication No. JP-H11-65569A